This invention relates to joist hangers, and in particular to improvements in hangers for wooden joists to properly seat and secure the joist in the hanger.
Metal hangers are widely used in wood frame construction to attach joists to carrying members. These hangers typically comprise an upright back, parallel opposing sides forming a channel for receiving the joist, and a horizontal bottom extending forwardly from the back forming a seat for the joist. Some of these hangers also have a flange extending rearwardly from the hanger for engaging the carrying member. Some of these hangers may also have holes provided to secure the hanger to the joist with screws or nails.
However, to save time and lower cost of installation it is preferable to avoid separately nailing or screwing each hanger to a joist, and thus hangers have been constructed to self-secure a joist inserted into the hanger. For example, the sides of some hangers are constructed to frictionally grip a joist inserted into the hanger. Another example is the hanger in Gilb, U.S. Pat. No. 3,663,950, which has a retainer member formed as part of the sides of the hanger and blunt-faced cutting teeth for cutting a groove in the joist for the retainer member. A problem with these prior self-secure type hangers, however, has been their inability to readily accommodate typical dimensional variances among joists of the same nominal size which arise from dressing tolerances and wood swelling and shrinkage. These prior self-secure hangers are difficult to put on slightly oversized joists and difficult to keep on slightly undersized joists.
Because a large number of hangers may be needed in a structure, it is important to minimize the cost of the hangers. However, the types of hangers presently in use generally must be carefully sized and formed to properly engage the joist, and thus the hangers can be expensive. It is also important that the hangers secure the joist and prevent the joist from working free from the hanger. However, in hangers employing a frictional grip the joist can work free, especially during the rough handling they are likely to receive on a construction site. The joist must be properly seated for the hanger to properly secure the joist. However, it is sometimes difficult to properly insert the joist into the hanger, and if the end of the joist is not carefully aligned with the back of the hanger as the joist is inserted into the hanger, the joist will not be properly seated. Thus proper engagement between the hangers and the joists requires careful installation which is expensive and time consuming.
It is therefore among the objects of the present invention to provide a self-secure type joist hanger that can accommodate typically encountered variances among joists of the same nominal size; to provide such a hanger that is of simple and inexpensive construction and which does not require precise forming; to provide such a hanger that secures the joist and prevents the joist from working out of the hanger, even during rough handling; and to provide such a hanger that helps to properly seat the joist in the hanger, without careful alignment or special effort by the installers.
Generally, the joist hanger of the present invention comprises an upright back, parallel opposing sides forming a channel and a horizontal bottom extending forwardly from the back forming a seat for the joist. At least one pair of opposing tabs extends inwardly from the sides of the hanger into the channel to present downwardly, rearwardly sloping surfaces to a joint forced against the tabs, to urge the joist against the back of the hanger. The innermost edge of each tab is knife-like, for penetrating the joist forced against the tab. The tabs are preferably formed from portions of the sides folded inwardly along downwardly, rearwardly sloping fold lines. Each fold line preferably extends from the base of a slit in the side to a point on the front edge of the side above the base of the slit. The slit preferably extends reardwardly, parallel to the horizontal bottom. The tabs are therefore triangular, having an apex extending into the channel and acting like a barb to engage the joist and prevent its escape from the hanger.
Other objects and features will be in part apparent and in part pointed out hereinafter.